Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$114.74	10.318%	$126.5789	$126.58	$126.60	$126.60
Purchase #2	$83.72	5.421%	$88.2585	$88.26	$88.25	$88.30
Purchase #3	$177.90	10.315%	$196.2504	$196.25	$196.25	$196.30
Purchase #4	$170.85	9.601%	$187.2533	$187.25	$187.25	$187.30
Purchase #5	$240.60	7.237%	$258.0122	$258.01	$258.00	$258.00
Purchase #6	$126.27	7.751%	$136.0572	$136.06	$136.05	$136.10
Purchase #7	$185.90	5.658%	$196.4182	$196.42	$196.40	$196.40
7 purchase totals =	$1,099.98		$1,188.8287	$1,188.83	$1,188.80	$1,189.00